Although the braking performance on a WET road surface (that is, a wet road surface) of tires attached to an actual vehicle has been conventionally evaluated by attaching actual tires to the vehicle and traveling the vehicle, this evaluation method has a problem in that the test cost is expensive.
Accordingly, there are methods as described in PTL 1 and PTL 2 that construct a tire model, a road surface model, and a fluid model in which a water film between tires and the road surface is modeled and perform simulation using these models. However, since the calculation costs of these methods are high, they are not suited for analysis combined with a vehicle model.
In addition, there is a known method as described in PTL 3 and PTL 4 that acquires a μ-S curve representing the relationship between a friction coefficient μ and a slip ratio S of a tire by using a tire model (brush model) in which a brush-like elastic element corresponding to a tread rubber is radially pasted to the outer periphery of a cylindrical belt.
PTL 1: JP-A-2002-14011
PTL 2: JP-A-2004-338660
PTL 3: JP-A-2007-203809
PTL 4: JP-A-2003-57134